Modelling anisotropic viscous flow
Fluid-like movements in the Earth’s mantle largely depend on the rheological behaviour of olivine, the main rock-forming mineral in the upper mantle. Although the mantle’s average viscosity can be inferred from post-glacial rebound and geoid anomalies, the micromechanical mechanisms that enable deformation of the solid mantle are identified from rock‑mechanics experiments. Dislocation creep emerges as the predominant deformation mechanism in the uppermost mantle, aligning olivine crystals into a crystallographic preferred orientation (CPO) parallel to the flow. This alignment produces anisotropic viscous behaviour, which in turn affects the deformation. Thus, anisotropic viscosity and CPO evolve together and can have a significant role in the dynamics of the upper mantle.
In this talk, I will summarise previous efforts to model anisotropic viscosity and texture evolution during geodynamic and tectonic processes. I will then present a new, efficient method for modelling CPO evolution and the resulting anisotropic viscosity in a fully coupled way within geodynamic simulations. Finally, I will discuss links between geodynamic and ice‑dynamics simulations and the potential role of anisotropic viscosity in these systems.
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